{ "id": "stoichiometry", "version": "898132e0da14", "status": "published", "name": "Stoichiometry Calculator", "question": "What does stoichiometry predict?", "summary": "Balances a chemical equation and turns a known mass or number of moles of one substance into the moles and grams of every other substance in the reaction.", "category": "chemistry", "subcategory": "stoichiometry", "url": "https://www.acalculator.org/chemistry/stoichiometry-calculator", "markdown": "https://www.acalculator.org/chemistry/stoichiometry-calculator.md", "kind": "function", "method": "Balance the equation; known moles n = grams ÷ molar mass (or as typed); moles of X = n × (coefficient of X ÷ coefficient of the known); grams of X = moles of X × molar mass of X.", "assumptions": [ "The reaction goes to completion as written, and the known substance sets the amount (no limiting reactant check).", "Molar masses use the CIAAW 2024 abridged standard atomic weights; electrons count as having no mass." ], "inputs": { "$schema": "https://json-schema.org/draft/2020-12/schema", "type": "object", "properties": { "eq": { "title": "Chemical equation", "description": "The reaction, balanced or not: formulas joined by +, with = or → between the reactants and the products.", "type": "string", "maxLength": 300 }, "k": { "title": "Known substance", "description": "The formula of the substance whose amount you know, as it appears in the equation.", "type": "string", "maxLength": 60 }, "n": { "title": "Known amount", "description": "How much of the known substance, in the unit chosen below.", "type": "number", "exclusiveMinimum": 0, "maximum": 1000000000000 }, "u": { "title": "Amount in", "description": "Grams or moles.", "type": "string", "enum": [ "g", "mol" ] }, "t": { "title": "Find", "description": "The formula of the substance to find, as it appears in the equation.", "type": "string", "maxLength": 60 } } }, "outputs": { "targetMass": { "label": "Mass to find", "description": "Moles to find × its molar mass.", "format": "number" }, "targetMoles": { "label": "Moles to find", "description": "Known moles × (its coefficient ÷ the known coefficient).", "format": "number" }, "knownMoles": { "label": "Known moles", "description": "The known amount in moles: grams ÷ molar mass.", "format": "number" }, "knownMass": { "label": "Known mass", "description": "The known amount in grams: moles × molar mass.", "format": "number" }, "balanced": { "label": "Balanced equation", "description": "The equation with the smallest whole-number coefficients.", "format": "text" }, "ratio": { "label": "Mole ratio", "description": "Moles to find per mole of the known substance.", "format": "text" }, "all": { "label": "Every substance", "description": "The moles and grams of each substance for this amount of reaction.", "format": "text" } }, "defaultAnswer": { "inputs": { "eq": "C3H8 + O2 = CO2 + H2O", "k": "C3H8", "n": 44, "u": "g", "t": "CO2" }, "outputs": { "targetMass": 131.73658071977687, "targetMoles": 2.993400911626641, "knownMoles": 0.9978003038755471, "knownMass": 44, "balanced": "C₃H₈ + 5O₂ → 3CO₂ + 4H₂O", "ratio": "3 mol CO₂ per 1 mol C₃H₈", "all": "C₃H₈: 0.9978 mol, 44 g; O₂: 4.989 mol, 159.638 g; CO₂: 2.9934 mol, 131.737 g; H₂O: 3.9912 mol, 71.9015 g" }, "text": "44 g (0.9978 mol) of C3H8 gives 131.737 g (2.9934 mol) of CO2." }, "examples": [ { "given": { "eq": "Al + I2 = AlI3", "k": "Al", "n": 0.429, "u": "mol", "t": "I2" }, "expect": { "targetMoles": 0.6435, "balanced": "2Al + 3I₂ → 2AlI₃" }, "source": "OpenStax, Chemistry 2e, §4.3 Reaction Stoichiometry, https://openstax.org/books/chemistry-2e/pages/4-3-reaction-stoichiometry (Example 4.8: 0.429 mol Al × 3 mol I₂ ÷ 2 mol Al = 0.644 mol I₂); hand calculation in content.mdx: 0.429 × 3 ÷ 2 = 0.6435" }, { "given": { "eq": "MgCl2 + NaOH = Mg(OH)2 + NaCl", "k": "Mg(OH)2", "n": 16, "u": "g", "t": "NaOH" }, "expect": { "targetMass": 21.94660402270272, "knownMoles": 0.2743531267682916 }, "source": "OpenStax, Chemistry 2e, §4.3 Reaction Stoichiometry, https://openstax.org/books/chemistry-2e/pages/4-3-reaction-stoichiometry (Example 4.10: about 22 g NaOH); CIAAW, Abridged Standard Atomic Weights (2024), https://ciaaw.org/abridged-atomic-weights.htm; hand calculation in content.mdx: 16 ÷ 58.319 × 2 × 39.997 = 21.947 g", "tolerance": 1e-12 }, { "given": { "eq": "C8H18 + O2 = CO2 + H2O", "k": "C8H18", "n": 702, "u": "g", "t": "O2" }, "expect": { "targetMass": 2458.0016982982, "balanced": "2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O" }, "source": "OpenStax, Chemistry 2e, §4.3 Reaction Stoichiometry, https://openstax.org/books/chemistry-2e/pages/4-3-reaction-stoichiometry (Example 4.11: 2.46 × 10³ g O₂); CIAAW, Abridged Standard Atomic Weights (2024), https://ciaaw.org/abridged-atomic-weights.htm; hand calculation in content.mdx: 702 ÷ 114.232 × 25 ÷ 2 × 31.998 = 2,458.0 g", "tolerance": 1e-12 }, { "given": { "eq": "C3H8 + O2 = CO2 + H2O", "k": "C3H8", "n": 44, "u": "g", "t": "CO2" }, "expect": { "targetMass": 131.73658071977684, "targetMoles": 2.993400911626641 }, "source": "OpenStax, Chemistry 2e, §4.3 Reaction Stoichiometry, https://openstax.org/books/chemistry-2e/pages/4-3-reaction-stoichiometry (Example 4.9: C₃H₈ + 5O₂ → 3CO₂ + 4H₂O); CIAAW, Abridged Standard Atomic Weights (2024), https://ciaaw.org/abridged-atomic-weights.htm; hand calculation in content.mdx: 44 ÷ 44.097 × 3 × 44.009 = 131.74 g", "tolerance": 1e-12 } ], "sources": [ "OpenStax, Chemistry 2e, §4.3 Reaction Stoichiometry, Examples 4.8 (aluminium and iodine), 4.9 (propane), 4.10 (magnesium hydroxide) and 4.11 (octane). https://openstax.org/books/chemistry-2e/pages/4-3-reaction-stoichiometry (retrieved 2026-10-01)", "CIAAW (Commission on Isotopic Abundances and Atomic Weights), Abridged Standard Atomic Weights, 2024. https://ciaaw.org/abridged-atomic-weights.htm (retrieved 2026-10-01)" ], "related": [ "chemical-equation-balancer", "molar-mass", "molarity" ], "changelog": [] }